from __future__ import annotations

text: str

with open("input.txt") as f:
    text = f.read()

points: list[list[int]] = [list(map(int, line.split(","))) for line in text.splitlines()]

max_area: int = 0
for i, point in enumerate(points):
    x, y = point
    areas: list[int] = []
    for x2, y2 in points:
        areas.append(abs(((x - x2) + 1) * ((y - y2) + 1)))
    max_area = max(max(areas), max_area)

print(max_area)